Which player do you use now?
If you are interested in the X3 because 24Bit, let me tell you it's absolutely not worth it! I have never met a person that claimed it could tell the difference between 16 and 24 bit from the same source. I have done this blind test multiple times and it's simply not audible. (Dolby has discovered that lower sampling rates create more brain usage although a difference was inaudible but the test was 128k mp3 vs CD. So at CD quality the brain does not need to fill in any gaps. 24 Bit is multiples of overkill.)
So unless your source is lacking amplification wise (background hiss, distortion, high output impedance) there is not much use.
I would not "upgrade" from FiiO E17 or iDevices. The result will be too similar. Actually I found the combo iPhone+E17 better.
But go ahead and purchase if you don't have a portable media player yet.
As mentioned, the user interface is pretty outdated and there are still plenty of bugs that need to be fixed.
I hope both issues will be resolved in the future, but I would not bet on it.